This invention relates to an image processing device for processing an input image or image given as data in the most suitable manner, an image recording apparatus such as a multicolor copying machine which has the image processing device and forms a multicolor image by recording images of every color component with use of a plurality of photosensing drums and overlaying the read images, and an image forming apparatus.
In the conventional printing field or in the industry of hard-copy machines such as a printer and a digital copying machine, a so-called line pattern image recording technique has been known. The line pattern image recording technique is a method of representing an image by a pattern constituted of a group of lines arranged in parallel periodically as shown in FIG. 20. Each of the lines is constituted of pixel values of a plurality of pixels arranged in a vertical direction, and the widths of the lines represent the gradation of the image.
According to the line pattern image recording technique, it is in the vertical direction that dots (pixels) are adjacent to each other in the vertical direction, thereby the frequency of the dot pattern is made so low that the density of the recorded image is made stable. Further, such a periodic texture is generally not recognized as noise, and thus a texture apparently having less noise can be obtained.
According to method of recording the line pattern, with use of an image recording device driving pulse generation means capable of controlling the reference position (starting position) of a driving pulse for driving the image recording device in units of a pixel, the reference positions of the recording device driving pulse of even pixels and odd pixels are respectively defined as front reference positions and back reference positions to form a pattern as shown in FIG. 21, thereby a line pattern having a two-pixel period is obtained (Japanese Patent Publication No. 5-80862).
According to the above-mentioned conventional method however, only a line pattern having a two-pixel period can be obtained. In addition, the desirably inclined and smooth line pattern necessary in the multicolor recording cannot be formed according to this method.